Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
# /usr/bin/python
# -*- coding: utf-8 -*-
#
import sys


H,W = map(int, input().split())
num_w = -1
srch = []
for i in range(H):
  h = list(str(sys.stdin.readline().rstrip()))
  for j in range(W):
    if h[j] == ".":
      srch.append([i+1,j+1])
      num_w += 1

Cn = [[sys.maxsize for j in range(W+2)] for i in range(H+2)]
Cn[1][1] = 0
for _ in range(num_w):
  for i,j in srch[1:]:
    Cn[i][j] = min(Cn[i-1][j],Cn[i][j-1],Cn[i+1][j],Cn[i][j+1])+1

if Cn[H][W] < sys.maxsize:
  print(num_w - Cn[H][W])
else:
  print(-1)